Silica-alumina-gallium oxide catalyst and method of preparation thereof



United States Patent 3,198,749 SILICA-ALUMlNA-GALLIUM OXIDE CATALYST AND METHOD OF PREPARATION THEREGF -Elr0y Merle Gladrow, Edison Township, Middlesex County, N.J., and Richard Joseph De Feo, Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed Oct. 10, 1960, Ser. No. 61,340 4 Claims. (Cl. 252453) The present invention relates to the preparation of improved cracking catalysts containing silica and alumina.

According to the present invention stable silica-alumina cracking catalysts having high percentages of alumina are prepared which are more selective and active than conventional commercial catalysts and more selective and active than catalysts prepared according to the prior art teachings. These new catalysts have a complete dis-persion of the alumina and silica in the catalyst, have high acid strength stability and high surface area retention after steaming compared to conventional commercial silica-alumina cracking catalysts.

In one form of the invention the silica alumina gelled composite containing a high percentage of alumina is aged at room temperature for an extended period of time.

In another form of the invention a superior high alumina content silica-alumina cracking catalyst is made by hydrolyzing a non-aqueous mixed solution of organic silica and aluminum compounds, treating with a gaseous acid such as HCl, preferably CO and then with an aqueous solution of an acid.

In another form of the present invention the silicaalumina catalyst containing a high percentage of alumina was prepared by mixing a silica hydrosol with an organic aluminum salt such as aluminum citrate or tartrate.

In another form of the present invention the silicaalumina catalyst containing a high percentage of alumina contained gallium oxide.

In the course of a study of the fundamental properties of cracking catalysts it has been found that, with silicaalumina catalysts, the performance of the finished catalyst in a cracking operation is dependent upon certain properties (physical and chemical) which the catalyst has and which are built into the catalyst by the particular procedure or process used in the preparation of the catalyst. For instance, it has been found that it is important that a catalyst have high acid strength and titer, high stability of surface area and acidity when the catalyst is subjected to steam, and a complete dispersion of the alumina throughout the amorphous silica network so that no alumina crystallites are observed by X-ray diffraction techniques.

Silica-alumina catalysts containing high percentages of alumina and comprising about 0.8 A1 atoms per Si atom or about 40 wt. percent A1 0 have been made by a variety of techniques and their cracking and physical properties studied. Heretofore these catalysts have shown, in general, a higher activity (conversion at a specified feed rate) and a somewhat higher surface area stability towards steam but they have also been notorious for producing more C gas and coke than standard conventional silicaalumina catalyst containing 13% A1 0 In addition all of the prior commercial silica-alumina catalysts containing high percentages of alumina which have been examined by X-ray diffraction have shown crystalline alumina in the composite Alumina is a cracking catalyst in its own right, but catalyzes cracking by a different mechanism than mixed oxide acidic catalysts, giving high selectivity towards C gas and carbon or coke in the cracked products.

With cracking catalysts of the mixed oxide type it is i essential to have a high degree of dispersion or complete dispersion of the minor oxide component throughout the framework of the major oxide component and to have a high acid strength and high acid strength retention after heating and/or steaming, and high surface area retention after heating and/or steaming.

It has been known for some time that high alumina silica-alumina type catalysts exhibit high activity relative to conventional commercial 13% Al O SiO catalysts, particularly after steaming. But this higher activity is obtained at the expense of poor product distribution, inasmuch as the high alumina catalysts made relatively high coke and C gas. X-ray ditiraction patterns of these catalysts have heretofore always shown the presence of crystalline alumina. This suggests that the catalyst is not performing as efliciently as it might, but instead the crystal: line alumina cracks independently as a catalyst in its own right. Since alumina alone cracks hydrocarbons to give very high yields of coke and light gases, itis possible that the observed poor behavior of prior high alumina content silica-alumina catalysts could be due to the crystalline alumina present in the catalyst composite. This suggests that an improved high alumina catalyst would be one having a complete dispersion of the alumina (by exhibiting the lack of any crystalline alumina).

We have found recently also that the acid strength and titer of the active catalytic centers contribute to the quality of the products inasmuch as acidity bears on the relative amounts of the various reactions occurring in the over-all cracking operation. This has been shown to explain the diiference in the octane numbers of gasolines produced from the same feed stock using catalysts of different acid strength. Conventional SiO Al O catalyst containing 13% A1 0 has its acid strength and titer degraded by heat and steam so that activity is lost rather rapidly in a continuous cracking operation. It is apparent, then, that an improved catalyst over conventional SiO Al O (13% A1203) catalyst should have a higher acid stability while retaining acid strength when subjected to heat and/ or steam.

Surface area of catalysts is an important property, as it represents to some degree the amount of available space to permit reactions to occur. Silica-alumina catalysts in general undergo a continual decrease in surface area when subjected to heat and steam. The rate of surface area decline decreases as the alumina content increases. This suggests, then, that high surface area, and high surface area retention, which can be attained in high alumina-silica alumina catalysts is a very desirable feature.

According to the present invention an improved silicaalumina catalyst is made which contains a high percentage of alumina and which shOWS no crystalline alumina, has a high acid strength and titer, and a high surface area retention after steaming. With the present invention a silica-alumina catalyst containing a high percentage of alumina is produced which has improved selectivity and activity. One method for making such a catalyst employs an aging step carried out at room temperature for an extended period of time.

The aging or heat soaking step for the silica-alumina high alumina content catalyst is carried out after the silica-alumina composite or gel has its pH adjusted .to the range of 6.0 to 8.0, preferably to about 7.0. Within minutes after adjusting the pH the composite undergoes gelat-ion. The aging is carried out at room temperature for about 10 to 30 hours or possibly longer. During aging the alumina undergoes complete dispersion throughout the silica network which result is not obtained under other conditions.

The present invention is an improvement on Kimberlin et al. Patent 2,798,857, granted July 9, 1957. F01

sneavso lowing the general steps of this Kimberlin et al. patent and including the aging step of the present invention produces a highly active and selective catalyst.

EXAMPLE 1 A catalyst comprising about 40% A1 and 60% by weight of SiO;,, was prepared by mixing about 4.0 liters of freshly prepared silica hydrosol (3% SiO made by percolating sodium silicate solution over an acid form cation exchange resin, with about one liter of an 0.4 N NH OH solution. The silica hydrosol may have a pH between about 8 and 11.

The resulting silica hydrosol had a pH of about 8.5. To this mixture were added 0.92 liter of an anhydrous aluminum amylate solution (87 g. Al O /l.) using rapid and efiicient stirring. The aluminum amylate solution was prepared by dissolving 10 pounds of aluminum metal in 23 gallons of a 5050 mixture of mixed amyl alcohols and petroleum naphtha, the naphtha boiling in the range of 200 F. to 300 F. according to the method described in US. Patent 2,636,865 (taken from column 3 of Patent No. 2,798,857).

Stirring was accomplished by means of a propeller as set forth in Patent No. 2,798,857. By thus mixing the silica hydrosol and the anhydrous aluminum amylate solution with stirring, a hydrous slurry of silica-alumina particles was formed having a pH of about 8.55. After continued stirring for about minutes, 7.2 cc. of glacial acetic acid were added to lower the pH to about 7.0. After further continued stirring for about 4 or 5 minutes, the slurry set to a stiff gel. The alcohol and hydrocarbon solvent were drained off and rejected.

The gelled catalyst composite after standing for about an hour was oven dried at a temperature of about 250 F. for about 16 hours and then calcined for about 16 hours at about 1000 F. This catalyst is designated A and is a catalyst made without the aging step according to the present invention. This example also shows that the composite should not be dried before aging.

EXAMPLE 2 Another catalyst comprising about 40 wt. percent A1 0 and 60 wt. percent SiO was prepared according to the steps :set forth in Example 1 up to the preparation of the gel composite having a pH of about 7.0. The gelled silica-alumina catalyst prior to drying was left at room temperature (about 80 F.) for about 24 hours and then oven dried at 250 F. for about 16 hours. The dried gel was then calcined 16 hours at about 1000" F. This catalyst is designated B and sets forth one catalyst of the present invention. This catalyst also shows the advantage of not drying the catalyst before aging.

EXAMPLE 3 Another 40 wt. percent Al O -60 wt. percent SiO catalyst was prepared according to Example 2 except that after gelling at a pH of about 7.0, the gel composite was heat soaked for 3 hours at about 190 F., then cooled to room temperature (about 80 F.) and left at room temperature for about 24 hours. Then the gel composite was oven dried at about 250 F. for about 16 hours. The dried gel composite was then calcined for about 16 hours at about 1000 F. This catalyst is designated C.

EXAMPLE 4 The catalyst of this example is commercial conventional 13 wt. percent Al O -87 wt. percent SiO catalyst and is believed to be made by making a pumpable slurry of sodium silicate at a pH of about 7.0, impregnating the slurry with acid aluminum sulfate, ammoniating to restore the proper pH to precipitate the alumina and then spray drying. This catalyst was calcined for about 16 hours at atmospheric pressure at about 1000 F. This catalyst is designated D. This catalyst isnot a high alumina content silica-alumina catalyst.

EXAMPLE 5 Portions of catalysts A, B, C and D were steamed 24 hours at 1050 F. and atmospheric pressure and were examined by X-ray diffraction to determine if any alumina crystallites were present. The results are given in Table 1.

Table 1 Catalyst 'A I B i o l D A1 0 Crystallites present N 0 Yes The catalyst B of the present invention showed no A1 0 crystallites along with the conventional low alumina siiica-alumina catalyst.

EXAMPLE 6 Portions of Catalysts A, B, C and D were steamed 16 hours at 1050 F. and atmospheric pressure. The acid titer and acid strength distribution of the fresh and steamed catalysts was determined by means of a titration technique (H. A. Benesi, J. Phys. Chem., 61, 970 73 (1957), using n-butyl amine in a non-aqueous system and various Hammett indicators covering a wide acid Catalyst B of the present invention shows the best acidity retention of any of these catalysts after steaming and Catalyst D the poorest. Catalysts A and C are nearly as good as B on acidity retention. High acidity retention both in acid strength and titer is an indication of high activity of the steamed catalyst.

EXAMPLE 7 Portions of the fresh and steamed catalysts A, B, C and D were examined for cracking performance using pure cetane feed at 900 F. The results with the fresh catalysts is summarized below. The w./hr./w. is weight of feed per hour per weight of catalyst.

Catalyst A B O D Conversion, percent 50 50 50 W./l1r./W 4. 3 7.1 3.1 4.1 (l -Gas Yield, wt. percent 12. 4 9. 7 11.0 11. 0

Thus it is seen that the catalyst B of the present invention is more active and selective than any of the other catalysts.

The Catalysts A, C and D were tested after steaming for about 24 hours at about 1050 F. and atmospheric pressure as outlined above. The results follow:

Catalyst A B C D Conversion, Wt. Percent 30 30 30 3O W./hr./w 5. 7 6. 7 3.7 4. 1 C -Gas, Wt. Percent 5. 7 5. 5 5.0 5.5

Catalyst B is more active than the other catalysts.

The preferred Catalyst B was compared with a standard commercial 25% Al O SiO cracking catalyst in a fixed bed test with a gas oil feed. The catalysts Were shaped into ii by *7 pellets and steamed at 1050 F., 16 hours, 0 p.s.i. before testing.

5 Conditions: East Texas Light Gas Oil feed, 950 F 2 v./v./hr., 30 min. cycle (v./v./hr. is volume of liquid feed per volume of catalyst per hour) fi composite organic solution was left standing for 48 hours at room temperature and then hydrolyzed by slow addition with rapid stirring to a vessel containing 4000 ml. H and 25 ml. concentrated HCl to form a slurry of A percent with respect to 25% A1103 standard gelled Silica-alumina Particlescatalyst The mixture was then heat soaked for 3 hours at 170 0 190 F., cooled to room temperature and the pH ad- A 9 A A A A d to 6.8 1) addition of NH OH and then oven dried N hth G o b 0.N. lusts a 4 Version up a as a! on at 250 F. The catalyst composite was calcined 16 C t 1' t m9 M 5 hours at 1000" F. in amblentair and then placed in a vesa a VS i sel and subjected to an atmosphere of steam at 1050 F.,- 0 p.s.i.g. for 16 hours. This catalyst comprises 40% 1 Research 0.N.+3 ml. T.E.L. e of the isa- 323;222: 2 assesses5a.... a mventlon glves a f mgher converslo? .than w stand can be varied to give a silica alumina catalyst containing ard catalyst, along with improved selectivity as is shown between about 10 to 15% alumina by weight by the higher naphtha yield, lower gas and carbon production, and slightly higher octane number. Once again EXAMPLE 3 it is demonstrated that superior performance is obtain d C t l t E and F were titrated by the method of wlth catalyst B of the present mventwn- Benesi (J.A.C.S., 78, 5490 (1956); also I. Phs. Chem, 61,

EXAMPLE 8 970 (1957)), using butyl amine in a non-aqueous sys- 1 i A catalyst comprising 35% Al O -65% S10 was pre- Lem and Show the fol owmg relatmns pared in the preferred manner as given in Example 2 with A ,d M the proportions changed to give a 35 A1 0 Instead of Acid Strength Region, m using 4.0l1ters of silica hydrosol, about 4.9 liters of silica Percent H1 04 48 48 71 1 1 T 1 hydrosol were used. This catalyst is designated B-l. This 9 9 0m catalyst was steamed for 16 hours at 1050 at atmospheric Catalyst E (l 00 0' 05 0. 08 0. 00 0.13 pressure. Catalyst F 0.00 0. 00 0.13 0.13 0.26

EXAMPLE 9 V A standard commercial 25% 1 0 -75% 10 catalyst Thus'it is seen that the catalyst of the present invention, was steamed for 16 hours at 1050 F. at atmospheric f Shows a m higher acid titer after Steaming than pressure. This catalyst is designated B-2 commercial Catalyst E and in addition the remaining EXAMPLE 10 acid centers are at a much higheracid strength level.

Catalysts E and F were also examined by X-ray Catalysts A, B1 and B-2 were compared in a dilfraction methods to see if any crystalline alumina was fixed bed cracking test with the following results. present in the composite. Neither catalyst showed the Conditions: East Texas Light Gas Oil feed, 950 F., 2 presence of crystanme A1203 v./v./hr., 30 min. cycle 40 EXAMPLE 14 Catalysts E and F were tested in a cracking opera- Apmentwlth f Standard catalyst tron feeding pure cetane (N-C H at 900 F. The Catalyst following results were obtained.

A Con- A A A A version Naphtha Gas Carbon ON. 4; At Conversion A 17.9 0.0 0.0 0.3 0.3 13-1 119.6 +3.5 -3.4 1.1 ins 5. 52: 1 Research +3 ml. T.E.L. Catalyst 2. 2 8.8 20 These results show that a catalyst prepared according Catalyst F 20 to this form of the invention gives higher activity and conversion, with an improved product distribution com- These l Show the catalyst of the Pres ent mventlon 1s pared to the commercial 25% A1203 catalyst. The more active than the standard commercial catalyst and fened catalyst yields more naphtha less Carbon and gas, shows as good, if not better, selectivity characteristics. and gives a higher octane number than either the standard 55 EXAMPLE 15 catalyst B-Z or Catalyst A. This is believed to be due to a the improved dispersion of the A1 0 in the catalyst pre- P 5 25 i i Catalyst F and according to the present invention were eteimlne y t e BE met 0 usmg nitrogen adp sorption, both for the fresh catalyst after heatmg 16 hours EXAMPLE 11 at 1000 F. and also after steaming the catalysts for 16 The catalyst in this example is a commercially available h at 1050 and atmqsQhenc Pressure The P material comprising 13% Al O -87% SiO and similar to p rtionate amount of the orlgmal surface areas retalned Catalyst D of Example 4. This catalyst was subjected to after Smammg hr each catalyst 15 hsted below an atmosphere of steam at 1050 F., 0 p.s.i.g., for 24 Percent original hours. This catalyst is designated Catalyst E. sufrace area.

. retained EXAMPLE 12 I Catalyst E 45 A solution 6was plregllared bly (admumg 41161g.het1h )/l C t 1 t F 93 silicate and 1 00 m entaso mixe am aco os To this organic Solution were added, with ystirring, 920 Thus, the vastly improved stability of the catalyst of the ml. of an anhydrous aluminum alcoholate solution (equivalent concentration 87 gr. A1 0 per liter) in Pentasol. After stirring for an additional 10 minutes, dry HCl gas was bubbled into the solution or mixture for about 5 minutes at room temperature. The mixture or present invention to surface area loss by steam is demonstrated.

EXAMPLE 16 A O SiO cracking catalyst (B2) in a fixed bed test with the following results. Each catalyst was steamed at 1050 F., p.s.i.g., 16 hours prior to the test.

Conditions: East Texas Light Gas Oil feed, 950 F., 2

v./v./hr., 30 min. cycle.

A Percent with respect to 25% A1 0 standard catalyst (B-2) A con- A A A A version naphtha gas carbon 0 .N.

Catalyst F- +13. 9 +3. 5 3. 0 1. 2 +0. 5

1 Research O.N.-|-3 ml. Tun.

These results show that this Catalyst F of our invention gives a much higher conversion than the standard catalyst, along with higher yield of naphtha, lower gas and carbon, and a slight increase in octane number.

EXAMPLE 17 i For regeneration of cracking catalysts, it is preferred that they have a large pore volume. In this catalyst of the present invention the pore volume may be varied by controlling the amount of dry HClwhich is added during the preparation of the catalyst. Thus with the addition of more dry HCl, the pore volume increases. The amount of dry HCl referred to in Example 12 and below as limited addition is not sufiicient to cause gelation of the catalyst composite and when addition is complete, the solution remains clear. However, if additional dry HCl is added (approx. minutes of addition), the solution becomes cloudy and the material begins to gel. This degree of HCl addition is referred to as complete saturation in the example below.

. Chloride, 1101 Added I. V. Weight Percent Limited addition 0.31 0. 08 Complete saturation 0. 65 0. 06

eentails a simple and convenient method for preparing high alumina silica-alumina catalysts which are higlfly active and selective, and have the desirable properties of high acid strength and titer, low attrition rate, and good dispersion of the components throughout the catalyst composite. This method comprises (1) the formation of a homogeneous non-aqueous solution of the silica and alumina precursors, and (2) hydrolysis of the mixture to effect good dispersion of the components amongst each other. Catalysts so prepared have outstanding catalytic, physical and chemical properties.

In another form of the invention using organic silica and aluminum compounds the gaseous acid used is carbon dioxide. The CO gas causes partial gelation of the alumina and silica micelles and subsequent hydrolysis of the gel composite in a dilute aqueous acid solution followed by drying and calcining produces a superior catalyst. All acidic gases are not the equivalents of HCl gas or CO gas as will be shown hereinafter.

Carbon dioxide gas possesses decided advantages over HCl gas that make it a preferred material to use in manufacturing catalysts according to a method of the present invention. For example, no washing of the catalyst is required as there is when using HCl to remove residual chloride. Also the CO gas may be injected under pressure and subsequently recovered and recycled. The pos- 55% sibility of catalyst contamination from equipment corrosion is eliminated. In addition there is an economic and health advantage in using CO Catalyst E from Example 11 will be referred to in the next group of examples for purpose of comparison.

EXAMPLE 18 416 grams ethyl orthosilicate were diluted with 1600 cc. Pentasol. To this were added, with stirring, 920 cc. aluminum alcoholate solution (equiv. to 87 gr. Al O liter). The composite solution was then hydrolyzed in 4 liters of water containing 25 cc. concentrated HCl. The aqueous slurry was aged 16 hours at room temperature and then oven dried at 250 F. The oven dried material was steamed 16 hours at 1050 F. and atmospheric pressure. This catalyst comprises 40% Al O -60% SiO and is designated G.

EXAMPLE 19 416 grams ethyl silicate were diluted with 1600 cc. Pentasol. To this are added, with stirring, 920 cc. of aluminum alcoholate solution (equiv. to 87 g. Al O /liter). After admixture was complete, stirring was continued and S0 was bubbled through the solution for 10 minutes. The composite was then hydrolyzed in 4 liters of H 0 containing 25 cc. HCl, aged 16 hours at room temperature and oven dried at 250 F. The material was then steamed at 1050 F. for 16 hours at atmospheric pressure. This catalyst comprises 40% Al O -60% SiO; and is designated H.

EXAMPLE 416 grams ethyl silicate were diluted with 1600 cc. Pentasol. To this solution are added, with stirring, 920

cc. aluminum alcoholate solution (equiv. to 87 g. Al O liter). After admixture was complete, stirring was continued and CO bubbled through the solution for 10 minutes. Toward the later period of this CO treatment, the solution became considerably more viscous, indicating some sort of a gelation or polymerization taking place between the components. The composite was then hydrolyzed in 4 liters of H 0 containing cc. concentrated HCl, left to age 16 hours at room temperature and then oven dried at 250 F. The material was then steamed for 16 hours at 1050 F. and atmospheric pressure. This catalyst comprises Al O -60% SiO' and is designated I. It is one of the improved catalysts of the present invention.

EXAMPLE 21 Portions of Catalysts E, G, H and I after steaming were titrated by the method of Benesi (J.A.C.S., 78, 5490 (1956)), to determine their acid strength distributions.

Acid Titer, MeqJg. Acid Strength, Percent These data show the superiority in acid strength stability of Catalyst 1 over the other catalysts, including the standard commercial Catalyst E. The data also show the ability of C0 when added to the mixed organic solution of ethyl silicate and aluminum alcoholate in the preparation of the catalyst to impart superior acidity compared to S0 or no added gases. This high acidity stability makes itself manifest in the cracking operation.

The proportions of chemicals used in preparing the catalyst of Example 20 can be varied to give a silicaalumina catalyst containing between about 10% and by weight of alumina.

9 EXAMPLE 22 Catalyst: Standard roller attrition rate, percent/hr. Standard Catalyst E 3.7 Catalyst F employing dry HCl 3.4 Catalyst 1 employing CO 2.4

EXAMPLE 23 Catalyst 1 of our invention, prepared from ethyl silicate and aluminum alcoholate with :added CO was compared in a standard cetane cracking test with standard Catalyst E. Both catalysts were steamed at :1050" El, p.s.i.-g., for 16 hours prior to the test. The results are summarized below.

Catalyst: w./hr./w. to give 40% conversion Standard Catalyst E 2.3 Catalyst 1 6.3

The yields of carbon and naphtha were essentially equivalent .to the standard catalyst at these conversions but the yield of C dry gas was lower, 8% vs. 9% for the standard Catalyst E at 45% conversion.

Another highly active, selective, attrition resistant catalyst comprising silica-alumina was made by mixing silica hydrosol and an aluminum salt of an organic acid such as citric or tartaric. By means of this procedure any alumina content can be made and the resulting catalyst requires a minimum of washing or none. The catalyst is stable toward heat and steam and is more active than conventional silica-alumina cracking catalyst and just as selective. The catalyst is prepared from an organic acid salt of aluminum and an ammoniacal silica hydrosol.

Catalyst E from Example 11 will be referred to in the following examples for purposes of comparison.

EXAMPLE 24 An improved high A1 0 (40%)-Si0 cracking catalyst was prepared as follows. Four liters of a freshly prepared 3% silica hydrosol were added to one liter of a 0.33 N NH OH solution with stirring. The pH of the solution was 8.5. To this sol solution, was added slowly a solution comprising 340 g. aluminum citrate, 100 ml. cone. NH OH and 2 liters of water using good stirring. The mixture began to gel within minutes and CO (as 100 g. Dry Ice) was added to aid gelation. The final pH of the mixture was 6.0. The mixture was allowed to age 48 hours at room temperature and then dried at a temperature of 250 F. The catalyst was steamed for 16 hours at 1050" F., 0 p.s.i.g. before testing. This steam treatment simulates plant catalyst deactivation. This superior catalyst will hereafter be called Catalyst J.

EXAMPLE 25 W ./hr./w. to Gas Make Naphtha Catalyst give 43% at 43% Make at Conversion 43% The results above indicate that the higher activity, manifested in a higher feed rate to obtain the same conversion,

is accompanied by equivalent naphtha production, and as low, if not lower, gas make for the superior high alumina Catalyst J.

EXAMPLE 26 The surface acidity of Catalysts E and J was determined by titration in a non-aqueous system with butylamine. The results for the acidity measurements, after steam treatment, for these catalysts are given below.

Catalyst: Acidity, meq./ g. E 0.13 J 0.2-2

Again the superior high Al O -SiO Catalyst J shows its higher activity as shown in Example 25 in the higher surface acid titer.

EXAMPLE 27 A further example of the higher stability of the high A1 0 Catalyst J is shown in the percent retention of surface area after steaming as in Example 18. This is indicated below.

Percent original surface area Catalyst: retained after steaming E 45 J 74 EXAMPLE 28 Catalyst: Percent attrition in 1 hour E 3.7 J 2.7

Thus it can be seen that a superior high A1 0 content silica-alumina cracking catalyst may be prepared from the aluminum salt of an organic acid and a commercial silica hydrosol. This catalyst combines high activity with normal product distribution, stability, and improved catalyst strength.

Another highly active cracking catalyst showing a high selectivity to aromatic hydrocarbons and C plus naphtha contains a minor amount, up to 10%, of gallium oxide in a high alumina content silica-alumina catalyst. Dry gas yields on a weight basis are comparable or less than conventional silica-alumina catalyst containing about 13% alumina. This catalyst has a high acid titer and acid strength, as well as high surface area, low attrition rate, good heat and steam stability.

It is desirable to get complete dispersion of the alumina throughout the silica hydrogel or gel lattice so that there are no residues of crystalline alumina dispersed through the catalyst composite. In addition to these desirable physical and chemical properties it has been found that the cracking pattern of the catalyst can be changed or altered to favor the production of a higher proportion of naphtha of higher aromatic content without an increase in the yield of dry gas (wt. basis).

The catalyst may contain up to 10% by weight of gallium oxide, but preferably about 15% gallium oxide is used. The catalyst contains between about 10 and 50% alumina and the rest silica. It is preferred to add the gallium oxide at the time of mixing the solutions to produce the composite catalyst and not by impregnating an already finished silica-alumina gel or catalyst. This catalyst has the unexpected property of producing high aromatic content gasoline in a cracking operation. The catalyst may contain 20-45 parts by weight of alumina, 79-55 parts by weight of silica and 1-10 parts by weight of gallium oxide.

EXAMPLE 29 The catalyst of this example is the standard commercial catalyst comprising 13% Al O -87% SiO and similar to Catalyst D of Example 4. It is believed to ples below.

EXAMPLE 30 A fresh 3% silica hydrosol, made by the ion exchange method of Example 2, was prepared and 3.4 liters thereof were admixed with 20 ml concentrated NH OH and gave a resultant sol having a pH of 9.5. To this were added slowly and with stirring 640 ml of an aluminum alcoholate solution (equivalent to 87 gr. Al O /l.) and hydrolysis effected. To this mixed slurry were added 85 mol of a solution comprising gallium chloride (equivalent to 11.5 gr. Ga O The pH was adjusted to 7.0 with NH H, the composite heat soaked 3 hours at 170- 190 F. and cooled. The pH was readjusted to 7.0 with NH OH and the mixture oven dried at 250 F. and then calcined 16 hours at 1000 F. This catalyst is referred to in the subsequent example as Catalyst L. It comprises 33% A1 O -62% SiO -5% 62. 0

EXAMPLE 31 Catalysts K and L were each steamed 16 hours at 1050 F. and atmospheric pressure. When examined by X-ray, both catalysts showed no crystalline alumina present. Both catalysts were titrated with n-butyl amine in a non-aqueous system using the method of Benesi. The results are tabulated.

Acid Titer hleqJg. Acid Strength, Percent H1804 equiv.

48 48-71 71-91 91 Total Catalyst K" 0.00 0.05 O. 08 0. 00 0.13 Catalyst L 0. 03 0. 09 0.13 0. 00 O.

Thus it can be seen that the improved catalyst L of this invention is much more acidic than conventional catalyst GEIISQ EXAMPLE 32 Catalysts K and L after steaming as in Example 31 were tested in a cracking operation at 900 F., 10 minute cycle, using pure cetane feed. The following results were obtained.

Catalyst K L Conversion, Wt. Percent 31. 5 31. 5 W./hr./w 3. b 5. 2 (Ea-Gas, Wt. Percent 5. 7 5. 3 C5 Naphtha, Wt. Percent 15.0 15. 0

A fresh silica hydrosol (3% solids content) was made ammoniacal as in Example and aluminum alcoholate solution hydrolyzed therein. A dilute GaCl solution was added to the composite withstirring and the pH adjusted to about 6.8 with NH OH before oven drying at about 250 F. This catalyst was calcined at 1000 F. for 16 hours and is designated Catalyst M. The amounts of the reagents used were such as to give a composition to the catalyst of 68% SiO -31% Al O -1.0% Ga O EXAMPLE 34 Catalysts K and M were tested in a fixed catalyst bed reactor for their cracking properties using an East Texas Light gas oil feed, 950 F, and 30 minute cycle. The naphtha quality data follow.

The gas densities of the C materiais from both catalysts were in the range of 1.0-1.1 based on air density equal to unity. Thus it is seen that with as little as 1% 6&203 added a marked increase in aromatics is produced with no change in gas density.

This form of the invention includes a high aluminasilica-alumina catalyst, a minor amount of gallia, preferably 15% which results in a catalyst producing naphtha of enhanced aromatic content with very little change, if any, in the weight of C gas and C naphtha yield.

The silica-alumina catalyst of the present invention may be made to contain between about 10% and by weight of alumina.

What is claimed is:

1. A catalyst composed essentially of 20 to 45 parts by weight of alumina, 79 to parts by weight of silica and 1 to 10 parts by weight of gallium oxide.

2. A catalyst consisting essentially of 33% A1 0 62% SiO -5% Ga O 3. A catalyst consisting of a major proportion of silica, at least 30% of alumina and 1%10% gallium oxide.

A method of preparing an active high alumina silica-alumina catalyst containing at least 25% alumina which comprises mixing ammoniacal silica hydrosol with aluminum alcoholate to hydrolyze the alcoholate and form a silica-alumina slurry, adding a gallium salt solution to said silica-alumina slurry in an amount sutricient to provide about 1 to 10% gallium oxide in the catalyst product,.aging the resulting slurry for at least 3 hours, and drying and calcining the aged slurry to produce a silica-alumina-gallium oxide catalyst consisting essentially of at least 25% alumina, 110% gallium oxide and at least 55% silica.

References Cited by the Examiner UNITED STATES PATENTS 1,935,177 11/33 Connolly et al. 252-455 X 2,412,958 12/46 Bates et al. 252453 2,470,193 5/49 Stratford 208-119 2,470,411 5/ 49 Corner 252457 2,485,260 10/49 Connolly 208-119 2,762,782 9/56 Kimberlin et al. 252-463 2,779,742 1/57 Emmett 252-455 2,784,147 3/57 Strecker et al. 252463 X 2,798,857 7/57 Kimberlin et a1 252453 2,809,169 10/57 Whiteley et al. 252453 X 2,814,599 11/57 Lefrancois et al. 252-455 X 2,859,185 11/58 Kimberlin et al. 252463 X 3,003,951 10/61 Winyall 252453 X MAURICE A. BRINDISI, Primary Examiner.

JULIUS GREENWALD, Examiner. 

1. A CATALYST COMPOSED ESSENTIALLY OF 20 TO 45 PARTS BY WEIGHT OF ALUMINA, 79 TO 55 PARTS BYWEIGHT OF SILICA AND 1 TO 10 PARTS BY WEIGHT OF GALLIUM OXIDE. 